There are double standards for judging the function of arc protection clothing

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Arc protection clothing arc protection ATPV EBT ASTMF1959

A common problem in the field of arc protection clothing is: whether the arc grade ATPV value or the arc grade EBT value can better reflect the clothing protective performance. As a standard related to human life, any wrong concept may lead to fatal injuries.

When ASTMF1959, the method for testing arc levels of clothing materials, was still in the development stage, Committee ASTMF18 (American Society for Experimental Materials Worker Electrical Protective Equipment Committee) recognized that, Some materials allow the skin to feel a warning of burning before the material breaks, while others do not. Therefore, two rating standards were initially produced: one is ATPV, arc thermal performance value; the other is EBT, material rupture threshold value. Experiments showed that each fiber broke before reaching the predicted level of combustion. Now, we find that knitted fabrics typically rupture before the burning point and woven fabrics burn before the rupturing point, and each fabric construction and type of fiber has its own pros and cons.

The committee renamed the arc class for two reasons: first, to simplify the terminology on the label for better understanding by end users, and second, to eliminate the Everyone has misconceptions about EBT. Considering many aspects, the committee retained the EBT and ATPV values as a label or appendix in the arc level, which is of great significance for the more professional and safe use of arc protection clothing. So now we can see that the labels of arc protection suits are marked with ATPV=Xcal/cm2 or EBT=Xcal/cm2.

In most cases, fabrics marked with EBT values do not show second-degree burns on the calorimetric sensor because the tiny cracks in the fabric are not directly located. on the sensor. Theoretically, if these crack holes were located directly on the sensor, there would be a burn predicted in the place of the crack hole, so the rating could be made directly. Both arc levels are measured in cal/cm2 and the smaller value is usually recorded. In other words, either the EBT value or the ATPV value can be recorded, but in the end only one is selected as the arc grade assessment of the fabric. According to ASTMF1506 (Standard Performance Specification for Textile Materials Used in Protective Clothing Weared by Electrical Workers Exposed to Transient Arcs and Related Thermal Hazards) regarding arc levels, only the smaller value may be written on the garment label.

If the arc level of clothing is evaluated according to the ASTM F1506 standard, the fabric must undergo multiple tests. For example, the fabric must undergo a water washing test and an ASTM D6413 vertical burning test. In other words, for a fabric to truly be flame retardant under arc, flash fire or any flame conditions, it must comply with a series or more comprehensive tests.

The two indicators that define arc levels according to ASTM standards are as follows:

ATPV value According to the Storr curve, the energy incident on the material has a 50% probability of causing enough heat to penetrate the sample to cause second-degree burns.

The EBT value is the energy incident on the material that has a 50% probability of causing the sample to rupture. When the total area of holes produced in the fabric exceeds 1.6cm2, we consider it to be ruptured.

ATPV and EBT are both evaluated using the same test method (ASTMF1959), but the arc level is recorded using the value reached first. If the thermal insulation value of the material is greater than the arc tensile strength, the material will rupture first; otherwise, it will burn before it ruptures.

If the EBT value is equal to or less than the ATPV value, then “EBT” will be used as the arc level value and marked as arc level (EBT); if the EBT value is greater than ATPV value, then “ATPV” will be used as the arc level value and marked as the arc level.

We can also understand these levels from another perspective:

ATPV: In an 8-cal plain weave test, the likelihood of causing second-degree burns is 50%; EBT: In an 8-cal plain weave test, the likelihood of a 2.54cm crack in the material is 50%.

In practical applications, we cannot use ATPV value or EBT value to judge the quality of clothing protective performance, because they are “functionally equivalent”, two ratings There is no good or bad. Basically fabrics labeled “EBT” are generally more insulating than strong, while the reverse is true for fabrics labeled “ATPV”. If there is a difference, then the fabric marked “EBT” usually means that the garment is knitted and more comfortable to wear, but there is no essential difference between the two in terms of protection for the wearer.

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